x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 446 insertions, 0 deletions

diff --git a/net/mac80211/spectmgmt.c b/net/mac80211/spectmgmt.c
new file mode 100644
index 000000000..880f46257
--- /dev/null
+++ b/net/mac80211/spectmgmt.c
@@ -0,0 +1,446 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * spectrum management
+ *
+ * Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
+ * Copyright 2002-2005, Instant802 Networks, Inc.
+ * Copyright 2005-2006, Devicescape Software, Inc.
+ * Copyright 2006-2007  Jiri Benc <jbenc@suse.cz>
+ * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
+ * Copyright 2007-2008, Intel Corporation
+ * Copyright 2008, Johannes Berg <johannes@sipsolutions.net>
+ * Copyright (C) 2018, 2020, 2022-2024, 2026 Intel Corporation
+ */
+
+#include <linux/ieee80211.h>
+#include <net/cfg80211.h>
+#include <net/mac80211.h>
+#include "ieee80211_i.h"
+#include "sta_info.h"
+#include "wme.h"
+
+static bool
+wbcs_elem_to_chandef(const struct ieee80211_wide_bw_chansw_ie *wbcs_elem,
+		     struct cfg80211_chan_def *chandef)
+{
+	u8 ccfs0 = wbcs_elem->new_center_freq_seg0;
+	u8 ccfs1 = wbcs_elem->new_center_freq_seg1;
+	u32 cf0 = ieee80211_channel_to_frequency(ccfs0, chandef->chan->band);
+	u32 cf1 = ieee80211_channel_to_frequency(ccfs1, chandef->chan->band);
+
+	switch (wbcs_elem->new_channel_width) {
+	case IEEE80211_VHT_CHANWIDTH_160MHZ:
+		/* deprecated encoding */
+		chandef->width = NL80211_CHAN_WIDTH_160;
+		chandef->center_freq1 = cf0;
+		break;
+	case IEEE80211_VHT_CHANWIDTH_80P80MHZ:
+		/* deprecated encoding */
+		chandef->width = NL80211_CHAN_WIDTH_80P80;
+		chandef->center_freq1 = cf0;
+		chandef->center_freq2 = cf1;
+		break;
+	case IEEE80211_VHT_CHANWIDTH_80MHZ:
+		chandef->width = NL80211_CHAN_WIDTH_80;
+		chandef->center_freq1 = cf0;
+
+		if (ccfs1) {
+			u8 diff = abs(ccfs0 - ccfs1);
+
+			if (diff == 8) {
+				chandef->width = NL80211_CHAN_WIDTH_160;
+				chandef->center_freq1 = cf1;
+			} else if (diff > 8) {
+				chandef->width = NL80211_CHAN_WIDTH_80P80;
+				chandef->center_freq2 = cf1;
+			}
+		}
+		break;
+	case IEEE80211_VHT_CHANWIDTH_USE_HT:
+	default:
+		/* If the WBCS Element is present, new channel bandwidth is
+		 * at least 40 MHz.
+		 */
+		chandef->width = NL80211_CHAN_WIDTH_40;
+		chandef->center_freq1 = cf0;
+		break;
+	}
+
+	return cfg80211_chandef_valid(chandef);
+}
+
+static void
+validate_chandef_by_ht_vht_oper(struct ieee80211_sub_if_data *sdata,
+				struct ieee80211_conn_settings *conn,
+				u32 vht_cap_info,
+				struct cfg80211_chan_def *chandef)
+{
+	u32 control_freq, center_freq1, center_freq2;
+	enum nl80211_chan_width chan_width;
+	struct ieee80211_ht_operation ht_oper;
+	struct ieee80211_vht_operation vht_oper;
+
+	if (conn->mode < IEEE80211_CONN_MODE_HT ||
+	    conn->bw_limit < IEEE80211_CONN_BW_LIMIT_40) {
+		chandef->chan = NULL;
+		return;
+	}
+
+	control_freq = chandef->chan->center_freq;
+	center_freq1 = chandef->center_freq1;
+	center_freq2 = chandef->center_freq2;
+	chan_width = chandef->width;
+
+	ht_oper.primary_chan = ieee80211_frequency_to_channel(control_freq);
+	if (control_freq != center_freq1)
+		ht_oper.ht_param = control_freq > center_freq1 ?
+			IEEE80211_HT_PARAM_CHA_SEC_BELOW :
+			IEEE80211_HT_PARAM_CHA_SEC_ABOVE;
+	else
+		ht_oper.ht_param = IEEE80211_HT_PARAM_CHA_SEC_NONE;
+
+	ieee80211_chandef_ht_oper(&ht_oper, chandef);
+
+	if (conn->mode < IEEE80211_CONN_MODE_VHT)
+		return;
+
+	vht_oper.center_freq_seg0_idx =
+		ieee80211_frequency_to_channel(center_freq1);
+	vht_oper.center_freq_seg1_idx = center_freq2 ?
+		ieee80211_frequency_to_channel(center_freq2) : 0;
+
+	switch (chan_width) {
+	case NL80211_CHAN_WIDTH_320:
+		WARN_ON(1);
+		break;
+	case NL80211_CHAN_WIDTH_160:
+		vht_oper.chan_width = IEEE80211_VHT_CHANWIDTH_80MHZ;
+		vht_oper.center_freq_seg1_idx = vht_oper.center_freq_seg0_idx;
+		vht_oper.center_freq_seg0_idx +=
+			control_freq < center_freq1 ? -8 : 8;
+		break;
+	case NL80211_CHAN_WIDTH_80P80:
+		vht_oper.chan_width = IEEE80211_VHT_CHANWIDTH_80MHZ;
+		break;
+	case NL80211_CHAN_WIDTH_80:
+		vht_oper.chan_width = IEEE80211_VHT_CHANWIDTH_80MHZ;
+		break;
+	default:
+		vht_oper.chan_width = IEEE80211_VHT_CHANWIDTH_USE_HT;
+		break;
+	}
+
+	ht_oper.operation_mode =
+		le16_encode_bits(vht_oper.center_freq_seg1_idx,
+				 IEEE80211_HT_OP_MODE_CCFS2_MASK);
+
+	if (!ieee80211_chandef_vht_oper(&sdata->local->hw, vht_cap_info,
+					&vht_oper, &ht_oper, chandef))
+		chandef->chan = NULL;
+}
+
+static void
+validate_chandef_by_6ghz_he_eht_oper(struct ieee80211_sub_if_data *sdata,
+				     struct ieee80211_conn_settings *conn,
+				     struct cfg80211_chan_def *chandef)
+{
+	struct ieee80211_local *local = sdata->local;
+	u32 control_freq, center_freq1, center_freq2;
+	enum nl80211_chan_width chan_width;
+	DEFINE_RAW_FLEX(struct ieee80211_he_operation, he, optional,
+			sizeof(struct ieee80211_he_6ghz_oper));
+	struct ieee80211_he_6ghz_oper *_6ghz_oper =
+				(struct ieee80211_he_6ghz_oper *)he->optional;
+	DEFINE_RAW_FLEX(struct ieee80211_eht_operation, eht, optional,
+			sizeof(struct ieee80211_eht_operation_info));
+	struct ieee80211_eht_operation_info *_oper_info =
+			(struct ieee80211_eht_operation_info *)eht->optional;
+	const struct ieee80211_eht_operation *eht_oper;
+
+	if (conn->mode < IEEE80211_CONN_MODE_HE) {
+		chandef->chan = NULL;
+		return;
+	}
+
+	control_freq = chandef->chan->center_freq;
+	center_freq1 = chandef->center_freq1;
+	center_freq2 = chandef->center_freq2;
+	chan_width = chandef->width;
+
+	he->he_oper_params =
+		le32_encode_bits(1, IEEE80211_HE_OPERATION_6GHZ_OP_INFO);
+	_6ghz_oper->primary =
+		ieee80211_frequency_to_channel(control_freq);
+	_6ghz_oper->ccfs0 = ieee80211_frequency_to_channel(center_freq1);
+	_6ghz_oper->ccfs1 = center_freq2 ?
+		ieee80211_frequency_to_channel(center_freq2) : 0;
+
+	switch (chan_width) {
+	case NL80211_CHAN_WIDTH_320:
+		_6ghz_oper->ccfs1 = _6ghz_oper->ccfs0;
+		_6ghz_oper->ccfs0 += control_freq < center_freq1 ? -16 : 16;
+		_6ghz_oper->control = IEEE80211_EHT_OPER_CHAN_WIDTH_320MHZ;
+		break;
+	case NL80211_CHAN_WIDTH_160:
+		_6ghz_oper->ccfs1 = _6ghz_oper->ccfs0;
+		_6ghz_oper->ccfs0 += control_freq < center_freq1 ? -8 : 8;
+		fallthrough;
+	case NL80211_CHAN_WIDTH_80P80:
+		_6ghz_oper->control =
+			IEEE80211_HE_6GHZ_OPER_CTRL_CHANWIDTH_160MHZ;
+		break;
+	case NL80211_CHAN_WIDTH_80:
+		_6ghz_oper->control =
+			IEEE80211_HE_6GHZ_OPER_CTRL_CHANWIDTH_80MHZ;
+		break;
+	case NL80211_CHAN_WIDTH_40:
+		_6ghz_oper->control =
+			IEEE80211_HE_6GHZ_OPER_CTRL_CHANWIDTH_40MHZ;
+		break;
+	default:
+		_6ghz_oper->control =
+			IEEE80211_HE_6GHZ_OPER_CTRL_CHANWIDTH_20MHZ;
+		break;
+	}
+
+	if (conn->mode < IEEE80211_CONN_MODE_EHT) {
+		eht_oper = NULL;
+	} else {
+		eht->params = IEEE80211_EHT_OPER_INFO_PRESENT;
+		_oper_info->control = _6ghz_oper->control;
+		_oper_info->ccfs0 = _6ghz_oper->ccfs0;
+		_oper_info->ccfs1 = _6ghz_oper->ccfs1;
+		eht_oper = eht;
+	}
+
+	if (!ieee80211_chandef_he_6ghz_oper(local, he, eht_oper, chandef))
+		chandef->chan = NULL;
+}
+
+int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
+				 struct ieee802_11_elems *elems,
+				 enum nl80211_band current_band,
+				 u32 vht_cap_info,
+				 struct ieee80211_conn_settings *conn,
+				 u8 *bssid, bool unprot_action,
+				 struct ieee80211_csa_ie *csa_ie)
+{
+	enum nl80211_band new_band = current_band;
+	int new_freq;
+	int new_chan_no = -1, new_op_class = -1;
+	struct ieee80211_channel *new_chan;
+	struct cfg80211_chan_def new_chandef = {};
+	const struct ieee80211_sec_chan_offs_ie *sec_chan_offs;
+	const struct ieee80211_wide_bw_chansw_ie *wide_bw_chansw_ie;
+	const struct ieee80211_bandwidth_indication *bwi;
+	const struct ieee80211_ext_chansw_ie *ext_chansw_elem;
+	int secondary_channel_offset = -1;
+
+	memset(csa_ie, 0, sizeof(*csa_ie));
+
+	sec_chan_offs = elems->sec_chan_offs;
+	wide_bw_chansw_ie = elems->wide_bw_chansw_ie;
+	bwi = elems->bandwidth_indication;
+	ext_chansw_elem = elems->ext_chansw_ie;
+
+	if (conn->mode < IEEE80211_CONN_MODE_HT ||
+	    conn->bw_limit < IEEE80211_CONN_BW_LIMIT_40) {
+		sec_chan_offs = NULL;
+		wide_bw_chansw_ie = NULL;
+	}
+
+	if (conn->mode < IEEE80211_CONN_MODE_VHT)
+		wide_bw_chansw_ie = NULL;
+
+	if (ext_chansw_elem) {
+		new_op_class = ext_chansw_elem->new_operating_class;
+
+		if (!ieee80211_operating_class_to_band(new_op_class, &new_band)) {
+			new_op_class = -1;
+			if (!unprot_action)
+				sdata_info(sdata,
+					   "cannot understand ECSA IE operating class, %d, ignoring\n",
+					   ext_chansw_elem->new_operating_class);
+		} else {
+			new_chan_no = ext_chansw_elem->new_ch_num;
+			csa_ie->count = ext_chansw_elem->count;
+			csa_ie->mode = ext_chansw_elem->mode;
+		}
+	}
+
+	if (new_op_class < 0 && elems->ch_switch_ie) {
+		new_chan_no = elems->ch_switch_ie->new_ch_num;
+		csa_ie->count = elems->ch_switch_ie->count;
+		csa_ie->mode = elems->ch_switch_ie->mode;
+	}
+
+	/* nothing here we understand */
+	if (new_chan_no < 0)
+		return 1;
+
+	/* Mesh Channel Switch Parameters Element */
+	if (elems->mesh_chansw_params_ie) {
+		csa_ie->ttl = elems->mesh_chansw_params_ie->mesh_ttl;
+		csa_ie->mode = elems->mesh_chansw_params_ie->mesh_flags;
+		csa_ie->pre_value = le16_to_cpu(
+				elems->mesh_chansw_params_ie->mesh_pre_value);
+
+		if (elems->mesh_chansw_params_ie->mesh_flags &
+				WLAN_EID_CHAN_SWITCH_PARAM_REASON)
+			csa_ie->reason_code = le16_to_cpu(
+				elems->mesh_chansw_params_ie->mesh_reason);
+	}
+
+	new_freq = ieee80211_channel_to_frequency(new_chan_no, new_band);
+	new_chan = ieee80211_get_channel(sdata->local->hw.wiphy, new_freq);
+	if (!new_chan || new_chan->flags & IEEE80211_CHAN_DISABLED) {
+		if (!unprot_action)
+			sdata_info(sdata,
+				   "BSS %pM switches to unsupported channel (%d MHz), disconnecting\n",
+				   bssid, new_freq);
+		return -EINVAL;
+	}
+
+	if (sec_chan_offs) {
+		secondary_channel_offset = sec_chan_offs->sec_chan_offs;
+	} else if (conn->mode >= IEEE80211_CONN_MODE_HT) {
+		/* If the secondary channel offset IE is not present,
+		 * we can't know what's the post-CSA offset, so the
+		 * best we can do is use 20MHz.
+		*/
+		secondary_channel_offset = IEEE80211_HT_PARAM_CHA_SEC_NONE;
+	}
+
+	switch (secondary_channel_offset) {
+	default:
+		/* secondary_channel_offset was present but is invalid */
+	case IEEE80211_HT_PARAM_CHA_SEC_NONE:
+		cfg80211_chandef_create(&csa_ie->chanreq.oper, new_chan,
+					NL80211_CHAN_HT20);
+		break;
+	case IEEE80211_HT_PARAM_CHA_SEC_ABOVE:
+		cfg80211_chandef_create(&csa_ie->chanreq.oper, new_chan,
+					NL80211_CHAN_HT40PLUS);
+		break;
+	case IEEE80211_HT_PARAM_CHA_SEC_BELOW:
+		cfg80211_chandef_create(&csa_ie->chanreq.oper, new_chan,
+					NL80211_CHAN_HT40MINUS);
+		break;
+	case -1:
+		cfg80211_chandef_create(&csa_ie->chanreq.oper, new_chan,
+					NL80211_CHAN_NO_HT);
+		break;
+	}
+
+	/* capture the AP configuration */
+	csa_ie->chanreq.ap = csa_ie->chanreq.oper;
+
+	/* parse one of the Elements to build a new chandef */
+	memset(&new_chandef, 0, sizeof(new_chandef));
+	new_chandef.chan = new_chan;
+	if (bwi) {
+		/* start with the CSA one */
+		new_chandef = csa_ie->chanreq.oper;
+		/* and update the width accordingly */
+		ieee80211_chandef_eht_oper(&bwi->info, &new_chandef);
+
+		if (bwi->params & IEEE80211_BW_IND_DIS_SUBCH_PRESENT)
+			new_chandef.punctured =
+				get_unaligned_le16(bwi->info.optional);
+	} else if (!wide_bw_chansw_ie || !wbcs_elem_to_chandef(wide_bw_chansw_ie,
+							       &new_chandef)) {
+		if (new_op_class < 0 ||
+		    !ieee80211_operating_class_to_chandef(new_op_class, new_chan,
+							  &new_chandef))
+			new_chandef = csa_ie->chanreq.oper;
+	}
+
+	/* check if the new chandef fits the capabilities */
+	if (new_band == NL80211_BAND_6GHZ)
+		validate_chandef_by_6ghz_he_eht_oper(sdata, conn, &new_chandef);
+	else
+		validate_chandef_by_ht_vht_oper(sdata, conn, vht_cap_info,
+						&new_chandef);
+
+	/* if data is there validate the bandwidth & use it */
+	if (new_chandef.chan) {
+		/* capture the AP chandef before (potential) downgrading */
+		csa_ie->chanreq.ap = new_chandef;
+
+		while (conn->bw_limit <
+			       ieee80211_min_bw_limit_from_chandef(&new_chandef))
+			ieee80211_chandef_downgrade(&new_chandef, NULL);
+
+		if (!cfg80211_chandef_compatible(&new_chandef,
+						 &csa_ie->chanreq.oper)) {
+			sdata_info(sdata,
+				   "BSS %pM: CSA has inconsistent channel data, disconnecting\n",
+				   bssid);
+			return -EINVAL;
+		}
+
+		csa_ie->chanreq.oper = new_chandef;
+	}
+
+	if (elems->max_channel_switch_time)
+		csa_ie->max_switch_time =
+			(elems->max_channel_switch_time[0] << 0) |
+			(elems->max_channel_switch_time[1] <<  8) |
+			(elems->max_channel_switch_time[2] << 16);
+
+	return 0;
+}
+
+static void ieee80211_send_refuse_measurement_request(struct ieee80211_sub_if_data *sdata,
+					struct ieee80211_msrment_ie *request_ie,
+					const u8 *da, const u8 *bssid,
+					u8 dialog_token)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct sk_buff *skb;
+	struct ieee80211_mgmt *msr_report;
+
+	skb = dev_alloc_skb(IEEE80211_MIN_ACTION_SIZE(measurement) +
+			    local->hw.extra_tx_headroom);
+	if (!skb)
+		return;
+
+	skb_reserve(skb, local->hw.extra_tx_headroom);
+	msr_report = skb_put_zero(skb, IEEE80211_MIN_ACTION_SIZE(measurement));
+	memcpy(msr_report->da, da, ETH_ALEN);
+	memcpy(msr_report->sa, sdata->vif.addr, ETH_ALEN);
+	memcpy(msr_report->bssid, bssid, ETH_ALEN);
+	msr_report->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
+						IEEE80211_STYPE_ACTION);
+
+	msr_report->u.action.category = WLAN_CATEGORY_SPECTRUM_MGMT;
+	msr_report->u.action.action_code = WLAN_ACTION_SPCT_MSR_RPRT;
+
+	msr_report->u.action.measurement.dialog_token = dialog_token;
+	msr_report->u.action.measurement.element_id = WLAN_EID_MEASURE_REPORT;
+	msr_report->u.action.measurement.length =
+			sizeof(struct ieee80211_msrment_ie);
+	msr_report->u.action.measurement.msr_elem.token = request_ie->token;
+	msr_report->u.action.measurement.msr_elem.mode |=
+			IEEE80211_SPCT_MSR_RPRT_MODE_REFUSED;
+	msr_report->u.action.measurement.msr_elem.type = request_ie->type;
+
+	ieee80211_tx_skb(sdata, skb);
+}
+
+void ieee80211_process_measurement_req(struct ieee80211_sub_if_data *sdata,
+				       struct ieee80211_mgmt *mgmt,
+				       size_t len)
+{
+	/*
+	 * Ignoring measurement request is spec violation.
+	 * Mandatory measurements must be reported optional
+	 * measurements might be refused or reported incapable
+	 * For now just refuse
+	 * TODO: Answer basic measurement as unmeasured
+	 */
+	ieee80211_send_refuse_measurement_request(sdata,
+			&mgmt->u.action.measurement.msr_elem,
+			mgmt->sa, mgmt->bssid,
+			mgmt->u.action.measurement.dialog_token);
+}